Apparatus for sifting fine material



2 Sheets-Sheet 1 G. ROTH APPARATUS FOR SIFTIt G FINE MATERIAL Filed Sept3, 1921 Dec- 8, 1925- 8, I G. ROTH APPARATUS FOR SIFTING FINE MATERIALFiled Sept. 5, 1921 2 Sheets-Sheet z Patented Dec. 8, 1925.

UNITED STATES PATENT FFICE.

GEORG ROTH, OF DABMSTADT, GERMANY, ASSIGNOB TO GUSTAV STGCKLE, OFDARMSTADT, GERMANY.

APPARATUS FOR SIF'II'NG FINE MATERIAL.

Application filed September 3, 1921. Serial No. 498,476.

To all whom it may concern.

Be it known that I, Gnone ROTH, a citizen of the German Republic,residing at Darmstadt, Germany, have invented certain new and usefulImprovements in Apparatus for Sifting Fine Material (for which I havefiled applications in Germany, 1st of Dec. 1919, Patent No. 336,748,Germany 6th of April 1921, Italy, 28th of May 1921, France, 23rd May1921, Austria, 16th of April 1921, Hungary, 21st of April 1921,Czechoslovakia, 27th of April 1921), of which the following is a.specification.

Separating apparatus for separating fine materials is already knownwhich consists of a plurality of concentric receivers with spreadingplates and extending one within the other of which the innermost isformed for the supply of air for separating purposes through acentrifugal fan or blower located at its lower end and at its upper endfits in the annular space formed by two adjacent receivers.

In order to permit of operation of such separating apparatus with aircurrents blown therethrough and at the same time to obtain the maximumefiiciency in accordance with the invention the separation is effectedin several separate currents of which the main blown current strikes thematerial to be separated at right angles or approximately right anglesthereto and a weak current is blown through or several induced currentsare drawn through the coarse material already sifted by the centrifugalaction and the main current so that any fine material adhering to thecoarse material is separated out and led to the main current of air. Theadditional currents of air may be at an angle to the main current offlow in the same direction. By the repeated treatment of the coarsematerial a high output of fine ma terial is obtained. It is essentialthat the material to be separated and the air for separating purposesshould be separately supplied in order that the air only should enterthe centrifugal blower.

An improvement in the efliciency of the separating is effected byextracting separately therefrom any of the valuable fine materialcarried by the air current. This separation is effected by interceptingsuch fine material in the air current returning for commencement of itscycle again. imm di y bef re it ommen es the cycle,

Two embodiments of apparatus suitable for performance of the new methodare shown in the drawing in which Fig. 1 is a longitudinal sectionthrough one embodiment, Fig. 2 is a longitudinal section through thelower part of a second embodiment. Fig. 3 is a section on the line 11 ofFig. 1, Fig. 4 is a section on the line 2-2 of Fig. 1, and Fig. 5 is asection on the line 3-3 of Fig. 1 the centrifugal blower only beingshown.

As shown, the device consists of four concentric cylinders or casings a,b, 0, d of which the innermost a is expanded in the form of a cone atits upper end a and a conical downwardly projecting extension a thereofprojects in known manner into the annular space between the receivers oand d. The cylindrical part of the casing a extends towards the rotatingsuction pipe a Said pipe is carried by a rod 9 rotated by means of abelt pulley h or the like on the end of which is mounted a centrifugalblower e rotating with the tube a and serving to close the same.

The dish shaped blower e is fitted with a flat spreader plate 7 a coarsemeshed sieve e surrounding the outlet 0 (see also F 5) and openings 6 inthe lower wall. On the outer side of the suction pipe a are mounted inthe form of ribs several spreading plates z' which uniformly distributethe material to be sifted which passes through a tube is into theannular space between the receivers a and b and is supplied thereto bythe hopper Z. The casing 0 forms with the casings a and b the shiftingspace proper which tapers downwardly and terminates in a branch m forthe outlet of the coarse material.

In the upper part of the receiver 0 are located intercepting plates 12which prevent the particles thrown upwards or any heavy particlescarried upwards by the sifting current from passing over into the spacefor the fine material between the receivers 0 and cl. The receiver (Zforms the outer wall of the sifting apparatus. It tapers clownwardly toan outlet 0 for the fine material. In the cover of the casing d islocated a flap or valve 79 which when desired permits the inlet ofauxiliary air in regulatable manner.

In the wall a are provided strips 9 upturned and stamped out from thematerial inences thereof and beneath the hopper a is provided a receiverw across which extends an inclined wall a closing flap y being provided.

Sitting by means of the sifting apparatus shown in Figs. 1 and 2 iscarried out in the following manner.

The material to be sifted entering the inlet 7: passes into the hopper Zthence to the spreading plates 6 which rotate with the suction pipe aand is distributed in this manner uniformly over the whole surface ofthe spreading plate 7. As the centrifugal blower is so formed that themajor portion of the air flows vertically upwards such air strikes thematerial moving over the spreading plate 7 and throwsit outwards intothe annular space A between the receivers (L and Z). The coarse portionswhich are prevented by the sieve e from entering the blower falldownward beyond the blower and pass in front of the openings 6 of theblower from which a weaker current of air is directed. substantiallyhorizontally which current blows away any fine material adhering to theheavy particles and transfers it to the rising main current of air. Theresidue freed from fine material passes out at m and is fed to sacks orreturned for grinding. The fine material rises upward with thecompressed air and thus passes between the intercepting plates 01. Theseplates are formed with gaps and overlap so that any heavy particlesstill present are separated out without the air being too greatlyobstructed. At the upper part of the cone (1 the air and finematerialare separated, the line material falling largely due to the centrifugalaction and passing out through the outlet 0 while the air and a smallportion of the line material passes over the cone a into the suctionpipe a c and the cycle comagain. Any air passing away through the outlet0 is replaced by addi tional air entering the sifting apparatus throughthe valve or flap 7) in the cover of the casing. The valuable tinematerial carried forward by the returning compressed air into the hopperZ passes in front of the strips 9 and the fine material passes throughthe openings to behind the same into the re cciver a from which it canbe removed by opening the valve or flap g and the doors 2 and in thewalls of the receiver 0, (Z. The receiver .1; is made cylindrical sothat the sifting space proper A shall be cylindrical throughout.

In the embodiment shown in Fig. 2 the space traversed by the maincurrent of air is divided so as form a small suction chamber B in whichthe coarse material is freed from any fine material carried therewithand the fine material is transferred from the auxiliary air current intothe main air current. On the towel side of the open blower e arearranged bars or strips 6 preferably in line with the blower vanes.Beneath the blower the space A traversed by the main current is closedby a conical base which in the embodiment shown consists of a centraldished portion .9 and a conical plate 7" forming an extension thereofbut spaced therefrom at o.

On rotation of the blower the bars or strips 2? rotating above the innersurface of the dished portion 3 also exert a blowing action and a.negative pressure is produced in the space E beneath the conical base 8,r. Through the space 4; between the dished portion 8 and the plate 7*there is produced a current of air because the air in consequence of theinjector action due to the centrifugal action of the bars or strips 1 iswithdrawn from the space B. The coarse material tending to pass to theoutlet m is thus subjected in the space A to treatment by three currentsof air and passes into the space I) where it is subjected to a furthertreatment by air under negative pressure which separates any finematerial still adhering to the coarse material therefrom and leads it tothe main current of air in the space A.

I claim 1. An apparatus for separating fine material comprising incombination a cylindrical casing, a plurality of walls being arrangedconcentrically to said casing and suitably connected to each other, asuction pipe attached to a central driving axle and arranged. in linewith the shortened inner wall and having a disk shaped lower end. acentrifugal blower fixed to the lower end of the central axle near thelower opening of said suction pipe a rotatable member mounted on thelower end of said suction pi )e and. so fitted with a horizontal surfacethat the material which is supplied to said member will be dischargedcentrifugazlly from said member when the same rotates. a conical plateconnected to the bottom of said blower and being upwardly bentagainstsaid dish-shaped pipe so as to form a ring shaped outlet for thedistributing air current being produced by said blower, and

means for generating an auxiliary horizontal air current adapted to actupon the falling materials and to regain the liner particles from thecoarse material falling to the outlet, and means for separating the fineparticles from the air currents resuclied by said blower, substantiallyas set forth.

2. In a separating apparatus in combination with a closed cylindricalcasing titted with an outlet a feeding tube of said casing, a pluralityof concentric walls supported by said casing and covered by an uppercone -made in one piece with the feeding tube of said casing, a drivingaxle journalled in the cover of said casing, a suction pipe mounted onsaid axle, a blower fixed to the lower end of said axle and fitted withan upwardly inclined bottom plate, a distributing member attached to thelower end of said suction pipe and beneath the inner discharging channelsaid bottom plate having a circle of openings arranged near its upperedge and serving as passages for a Weak horizon tal branch air currentacting upon the ma.- terial falling into the discharge opening,

openings provided between the outer wall i and said cone for passing theair and fine particles to the outer channel having an outlet for thefine particles, and openings formed in said cone above a centralreceiver channel for line particles substantially as set forth.

3. In a separating apparatus in combination with a closed cylindricalcasing, a plurality of division-members, an axle journaled within saidcasing and fitted with means for discharging the materials bycentrifugal action, a blower attached to the lower end of said axle andadapted to generate a horizontal air current crossing the dischargedmaterial, a conical plate attached to the bottom of said blower andadapted to guide the air current, a shell fastened to the back of saidplate by means of interposed strips or blades for forming suctionchannels for an additional air current, a dished portion attached to theouter wall for restricting the passage for the coarse particles, so thatsaid passage is exposed to the action of a sucking air current, meansfor separating the fine particles from the rising air current, and meansfor discharging the line particles, substantially as set forth.

In testimony whereof I affix my signature.

GEO'RG ROTH.

